2-tert-butylphenol

Endpoint summary

Additional information

Several reliable (Klimisch 1 or 2) toxicity studies in fish, invertebrates, and algae have been conducted for o-tert-butylphenol and are included in this dossier.  Additionally, reliable toxicity studies with fish, invertebrates, algae, and microorganisms with the structural analogue, o-sec-butylphenol, have been included for supporting evidence. There were no reliable measured data for long-term toxicity to fish, however, modelled data are presented.

Reliable (Klimisch 1 or 2) short-term toxicity studies with fish have been conducted for o-tert-butylphenol and the structural analogue, o-sec-butylphenol and are included in this dossier.

The key study,Sasol (2013), provides a 96-hr LC50 of 2.682 mg/L for fish for o-tert-butylphenol

Consequently this value will be taken as the short-term toxicity in fish endpoint for o-tert butylphenol.

No reliable long-term toxicity studies with fish are available for o-tert-butylphenol. However modeled data are available and included in the dossier. Sasol (2013) provided a reliable (Klimisch 2) study for o-tert-butylphenol using the QSAR model, Ecological Structure Activity Relationships (ECOSAR) Class Program to estimate long-term toxicity to fish. The ECOSAR model estimates aquatic toxicity based on the structural similarity to chemicals for which aquatic studies are available.In addition, the log Kow and molecular weight of o-tert-butylphenol are within the criteria (max log Kow = 7 for acute, 8 for chronic and max molecular weight = 1000) and domain of the model.The measured log Kow of 3.3 was used in the model. Model results indicate a 30 day chronic value (the geometric mean of the NOEC and LOEC) to be 0.327 mg/L for phenol. As per REACH Guidance Ch 10, a NOEC can be calculated from the chronic value. Therefore, the calculated NOEC = 0.231 mg/L for the phenol category and consequently will be taken for the long-term toxicity to fish endpoint.

Reliable (Klimisch 2) short-term toxicity studies with invertebrates have been conducted for o-tert-butylphenol or the structural analogue, o -sec-butylphenol

and are included in this dossier. The key study, Schulz (1995), provides a 48-hr EC50 of 3.4 mg/L for o-tert-butylphenol for Daphnia magna. Additionally, McLeese et al (1981) provides a 96 -hr EC50 of 2.4 mg/L for o-tert-butylphenol for the saltwater shrimp. Consequently, these values will be taken as the short-term toxicity in aquatic invertebrates endpoint for o-tert-butylphenol.

Japan MOE (1999) conducted a reliable (Klimisch 1) GLP compliant long-term toxicity test following OECD 211 methods. Daphnia magna were exposed to measured concentrations of 0.0032, 0.01, 0.032, 0.1, 0.32, 1.0, and 3.2 mg/L of o-sec-butylphenol.  The 21-day NOEC based on reproduction was 0.32 mg/L. Consequently this value will be taken as the long-term toxicity in aquatic invertebrates endpoint for o-tert-butylphenol.

Adequate reliable measured data exists for toxicity to algae to o-tert-butylphenol and the analogue, o-sec-butylphenol. The data point of highest concern for this endpoint has been identified in a reliable study which reports a measured 72 hr EC50 of 6.5 mg/L and 72 hr EC10 of 2.0 mg/L, based on growth, for toxicity to aquatic algae. Consequently these values will be taken as the toxicity in aquatic algae endpoint for o-tert-butylphenol.

Horton et al. (1991) conducted a reliable study on the toxicity of the analogue, o-sec-butylphenol, to activated sludge microorganisms following OECD 209 guidelines. Activated sludge microorganisms were exposed to a control and 10 mg/L of the test substance for 3 hrs. Oxygen consumption was measured to determine the 3 hr EC50 of > 10 mg/L. Consequently, this value will be taken to fulfill the toxicity to microorganisms endpoint.